D&D 5E How do you make sewer dungeons believable?

[Scott Christian]

I like the historical perspective that cities are built upon cities of old. The sewers are sometimes old alleys and streets with some bricks for structural integrity. Sometimes they are washouts of a nearby ocean or aquifer. Sometimes they are old secret tunnels. And sometimes they are damp and tight, crowded and slimy and smelly, where characters are forced to walk in waste up to their knees while hunched over at a ninety degree angle. (Ugh. Just writing that grossed me out.)

 

[Benjamin Olson]

Well, returning to the Cloaca Maxima, not only was it unique to the capital, but considered a wonder of Roman urban ingenuity, such that it was not beneath the dignity of Augustus' right hand man Marcus Agrippa to personally inspect it in a row boat. It also had the benefit of a constant supply of aqueduct fed water from public baths and fountains flowing through to it, which kept it from becoming a stagnant, blocked up logjam.

Now, one could have the town be a former grand imperial capital, as some have suggested. While the presence of the papacy kept Rome from ever becoming a backwater it did drop to a population of 10,000 or so at several points (from an imperial peak of over a million), and parts of the city did at times become essentially small villages. Allegedly the Forum Romanum was actually used as a cattle field (though this is the sort of thing renaissance humanists and romanticist era historians would both be prone to exagerate for rhetorical effect).

Alternatively it could just be a very cramped and humble "sewer level". The most basic type of premodern closed sewer was where the ditches and streams that had formerly served as an open sewer were covered over for the sake of space and smell. In a fantasy world where sewers also breed monsters covering the open sewer would be an even higher priority. It need not be the full, fine stonework sewer we always see in media. Maybe the town just built a crude wooden covering over the stream they threw their wastewater in and a few ditches that fed into it. Maybe there is also access to crypts and basements of an old city there, or maybe it is a newer settlement. Maybe the sewer has been covered for a century or more and the town hasn't really thought of it since, or maybe it was all just done by some newly elected mayor who now needs the party's help because his whole, fancy show-off covered sewer project, that his opponents said was a pointless waste of time and timber, has lead to a wererat problem and he's up for reelection next year.

 

[Bedrockgames]

This is a silly setting problem to have, but it's recently come up in my megadungeon game. Or more specifically, in the small town beside the megadugenon. How do you make sewer dungeons believable?

To the best of my knowledge, medieval sewers were little more than open air ditches. Rome's Cloaca Maxima is a good model, but it's the sewage system of a world capital. I doubt that my little dungeon-adjacent village could justify such an engineering project. So when you're in a village setting rather than a major city, how do you justify sewer dungeons? Or are you better off inventing some other kind of subterranean labyrinth and saving yourself the verisimilitude hassle?

(Comic for illustrative purposes.)

You can be anachronistic if you want to be

 

[Xeviat]

My D&D setting is built on medieval/renaissance fantasy, not realism. Magical development is hand in hand with technological development. The existence of magic likely means certain technologies won't be necessary.

I once ran a sewer dungeon. The players needed to infiltrate a noble manor and their plan involved going through the sewers. The sewers in the noble district were elaborate, where they utilized gray oozes to feed on the waste and then used lye to neutralize the acidic run off before ejecting the salt water out to sea.

So, the party had to enter through the sea pipes. It functioned like a flooding room trap with the added danger of the water being acidic and the ticking timer of it about to get boiling and explosive. Then they had to deal with the gray oozes, which multiplied when hit with bladed weapons, which were all the group had.

It ended up being a real fun side adventure to send the group ninja and rogue on. At one point, the halflings rogue (who specialized in throwing darts and shuriken) rode on the human ninja's shoulders while the ninja wall ran around to avoid the oozes. They basically divided the oozes till they only had 1 hp and started actually dying when split.

I say just have fun with your sewers.

 

[jgsugden]

I ... don't. The sewars are not used in my campaign world as a dungeon source. In the rare place where storm drains or sewars exist they are too small for humanoid travels.

 

[Don Durito]

You just put them in. Then have them connect with something else - eg a buried former layer of the city.

If players say "Hey they didn't have any undergournd sewer systems in the middle ages" you say "what do you think this is? Ars Magica?".